1. Field of the Invention
The present invention relates to a solid-state imaging device and an imaging apparatus, and, more particularly to a solid-state imaging device as an example of a semiconductor device for physical quantity distribution detection that is formed by arraying plural unit elements, which have sensitivity to an electromagnetic wave inputted from outside such as light and radiation, and is capable of selecting, with address control, a physical quantity distribution converted into an electric signal by the unit elements and reading out the physical quantity distribution as the electric signal and an imaging apparatus including a mechanism same as that of the solid-state imaging device.
2. Description of the Related Art
In recent years, as an example of solid-state imaging devices, MOS (Metal Oxide Semiconductor) and CMOS (Complementary Metal-oxide Semiconductor) image sensors that can overcome various problems of a CCD (Charge Coupled Device) image sensor attract attention.
The solid-state imaging devices are widely used in recent years as imaging devices mounted on various portable terminal apparatuses such as a cellular phone and as image input devices (imaging devices) of imaging apparatuses such as a digital still camera and a digital video camera.
For example, a CMOS image sensor has an amplifier circuit including a floating diffusion amplifier for each of pixels. In reading out a pixel signal, as an example of address control, a system called column parallel output type or column type is often used. The column parallel output type or column type system is a system for selecting one row in a pixel array unit, simultaneously accessing the pixels in the one row, and reading out pixel signals from the pixel array unit in row units, i.e., simultaneously in parallel for all the pixels in the one row.
A solid-state imaging device may perform differential processing between a noise level (a reset level) and a signal level in a pixel signal voltage in order to remove a noise component included in a pixel signal corresponding to a signal charge amount acquired by a charge generating unit (photoelectric conversion means). This makes it possible to extract a signal component without the noise component from which the reset signal as the noise component is removed.
However, it has been found that, under a certain imaging condition, harmful effects are caused by performing such differential processing. Specifically, under an imaging condition in which an amount of light larger than an amount of light at a saturation level, for example, a high luminance object such as the sun or a light is present in a subject, when the extremely intense light is made incident on the charge generating unit, a reset level Srst of a pixel signal voltage changes (e.g., falls) as time elapses (the change is represented as ΔV). A signal component corresponding to a signal charge amount acquired by the charge generating unit (the photoelectric conversion means) is superimposed on a level lower by ΔV than the original reset level Srst immediately after the stop of application of a reset pulse. As a result, a signal level Ssig falls regardless of the fact that the intense light is irradiated. The high luminance object in the subject is photographed as a black image and an image quality is deteriorated.
A likely cause of this phenomenon is as described below. When intense light is made incident on the charge generating unit and the signal level Ssig reaches the saturation level, the signal level Ssig does not rise exceeding the saturation level and a fixed level is outputted. On the other hand, when more intense light is made incident on the charge generating unit and the reset level Srst falls, since the reset level Srst falls while the signal level Ssig remains fixed at the saturation level. Therefore, substantially, the signal level Ssig represented by a difference “Ssig−Srst” between the signal level Ssig and the reset level Srst falls.
Since the difference “Ssig−Srst” decreases regardless of the fact that the intense light is made incident on the charge generating unit, an image looks black regardless of the fact that the light is very bright, i.e., a blackening phenomenon (also referred to as darkening phenomenon) occurs.
In order to avoid such a blackening phenomenon, a mechanism has been devised which determines whether a pixel signal voltage is in a state of the blackening phenomenon, for example, whether a signal level is in a saturating area or whether a reset level is in a changing area and, when the blackening phenomenon is detected, prevents information of the blackening phenomenon occurrence from being transmitted to a post-stage circuit (see, for example, JP-A-2004-248304 and JP-A-2007-036916).